The invention relates to ventilation systems and to methods utilizing wind for ventilating enclosures.
Ventilation systems circulate air through enclosures including buildings, vehicles and other enclosures. Active ventilation systems rely on imported power. Passive ventilation systems rely upon system design to circulate air.
Some active systems rely on powered fans, heaters, air conditioners and humidity modifiers connected through a series of ducts. This approach has been successful in controlling the internal environment of buildings, private residences and vehicles, but may be complicated and energy demanding.
Passive systems, including those that passively derive operating energy from the environment, are often inefficient or ill-suited for demanding applications. In buildings with a plurality of floors and a high-profile there are few, if any, passive systems that adequately circulate air throughout the building.
In open buildings such as barns, sheds and the like, some passive systems have proved useful. Roof mounted xe2x80x9csquirrel cagexe2x80x9d wind turbines, for instance, exhaust internal air from the building under influence of the wind. During the summer, exhausting air from the roof cools the building by providing an escape for hot air trapped beneath the roof. Exhausting the hot air also fosters an internal air flow and circulation which results in a more comfortable environment.
Squirrel cage turbines are limited in efficiency for several reasons. The turbines rest directly on the roof line, which restricts their access to the turbulent eddies of disturbed air adjacent to the roof itself. This is especially pronounced for roofs with little or no pitch. For roofs with greater pitch, the short profile of standard squirrel cage turbines ensures that at least some will be located in the wind shadow of the roof itself. In systems having multiples of these turbines, the wind may race past the pitched roof and occasionally induce a reverse flow in some of the turbines, negating the beneficial action of the other turbines, and dramatically reducing the overall system efficiency.
Poor operating efficiency associated with systems having a plurality of squirrel cage turbines on a peaked roof results in an increased number of turbines and duct holes required to achieve the minimum desired air flow. Additional holes in the roof are not desirable for roofs where rain is common. Holes may compromise the structural integrity of the roof. Further, holes reduce the ability of the roof to insulate the building from cold or heat.
U.S. Pat. No. 4,957,037 discloses a Roof Ridge Ventilator, the disclosure of this patent is incorporated herein by reference. This ventilator is designed to inhibit the entry of wind-driven water into the structure. Unfortunately, the volumetric air flow capability of this vent is limited.
U.S. Pat. No. 5,655,964, incorporated herein by reference, discloses a Static Roof Ventilator having triangular baffles. The baffles improve the chimney effect of the ventilator. Still, there are many high-profile buildings that require more airflow than the ventilator of the ""964 patent can provide.
U.S. Pat. No. 5,711,480, incorporated herein by reference, discloses a control system for building ventilation. This control system relies on spread spectrum wireless communication between the components of the ventilation system in order to enable the system to operate efficiently without the need for complex, and expensive wiring.
What is desired is a ventilation system that is fuel efficient and can be used in buildings, or other enclosures, with high volumetric air flow needs.
A ventilation system for a building, or other structure includes a roof and an airfoil mounted on the roof. The airfoil includes a tubular member having a longitudinal axis, an inside, an outside, and an elongated opening extending parallel to the longitudinal axis. The air foil includes a leading edge positioned with respect to the longitudinal opening on the outside of the tubular member to create a pressure differential between the tubular member and the leading edge when wind blows past the airfoil. An air duct in communication with the interior of the tubular member extends into the building to enable the airfoil to draw air out from the building when the wind blows.
A control system including a valve is installed to modulate the air flow as desired for proper ventilation. Fully closing the valve protects against heat loss during cold weather. According to one aspect of the invention, the building includes an air conditioning system in communication with the control system. This valve can be either manually or automatically controlled and can be located within each individual airfoil""s duct system or as part of a larger plenum served by a plurality of airfoils.
According to another aspect of the invention, the building includes a duct forming a central air column within the building. The duct is regulated by the control system to seal in case of fire.